Multiple sources tell the magazine that Richards' health is at the center of the postponement. The ax-slinger is reportedly still getting back into form after falling out of a tree and injuring himself in 2006 in Fiji, while taking a break from the group's A Bigger Bang tour.

Richards admitted to late-night host Jimmy Fallon that he wasn't up to par in 2010.

"You are looking at a very rusty Keith Richards right now," Richards told Fallon. "If you've been on the road for two years and suddenly you stop, you put it down for a little bit. And then a little bit longer and you say, 'I really got to catch up, man.'"

In his defense, Richards has mustered up the energy to co-star in two "Pirates of the Caribbean" movies — and pen an autobiography, "Life" — in the years since the injury.